From : https://leetcode.com/problems/climbing-stairs/
You are climbing a stair case. It takes n steps to reach to the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
class Solution {
public:
int climbStairs(int n) {
if(n <= 0) return 0;
if(n <= 2) return n;
int pre = 1, post = 2, t;
for(int i=3; i<=n; i++) {
t = pre;
pre = post;
post = t + post;
}
return post;
}
};